The present invention relates to a network system for image data processing systems and data storage systems, in which access to data storage systems is controlled by bandwidth management means.
Devices for the real time storage of image frames, derived from video signals or derived from the scanning of cinematographic film, are disclosed in the present assignee""s U.S. Pat. No. 6,118,931. In the aforesaid patent, systems are shown in which image frames are stored at display rate by accessing a plurality of storage devices in parallel under a process known as striping.
Recently, there has been a trend towards networking a plurality of systems of this type, thus allowing systems to gain access to a number of different storage devices. However, accessing such storage devices at display rate requires expensive, high bandwidth networks.
Co-pending British patent applications 0008318.8, 0109753.4, and 2034-P564-GB describe methods of using a high bandwidth fibre channel switch, connected to a plurality of image processing systems and a plurality of redundant arrays of inexpensive disks (RAIDs), to convey image data over a high bandwidth channel without the cost of setting up a high bandwidth network. This is achieved by requesting access to data stored in a RAID controlled by another system.
Currently, such access involves the first processing system controlling a RAID allowing a second processing system unlimited access to the RAID for a short period of time before requesting the return of the RAID. This means that access by said second processing system can only take place when said first processing system is not accessing the RAID itself.
A networked image data processing environment, comprising a plurality of image data processing systems, a plurality of data storage systems, wherein each of said data storage systems is operated under the direct control of one of said image processing systems, a high bandwidth network connected to each of said data processing systems, a low bandwidth network connecting said image processing systems and said switching means, by which one of said processing systems controls the operation of said switching means, wherein a first processing system includes requesting means configured to request access to a data storage system controlled by a second processing system over said low bandwidth network, said second processing system includes bandwidth assessment means configured to assess an extent to which said second processing system requires access to said storage system; and comparison means configured to make an indication of storage regions that may be accessed if said extent is below a predetermined threshold.